The present invention relates to a method for the compression of images. It can be applied notably in the fields of the transmission or storage of images.
The compression of images consists in reducing the quantity of data elements needed to represent an image. Vector quantization, explained in the article by R. M. GRAY,"Vector Quantization", published in the IEEE journal, ASSP Magazine, Apr. 1984, is a method of image compression that has been widely used. This method consists in cutting up the image into blocks and in replacing each block by an index. This index relates to a dictionary containing a limited number of representative blocks. The dictionary is constituted according to the k-means algorithm developed in the article by J. MacQueen, "Some Methods For Classification And Analysis Of Multivariate Observations" published in the catalog, 5th Berkeley Symposium On Mathematics, Statistics And Probabilities, 1967, or according to the LBG algorithm explained in the article by Y. LINDE, A. BUZO, and R. M. GRAY, "An Algorithm For Vector Quantizer Design" in the IEEE journal, Communications, Jan. 1980.
The utility of the compression is nevertheless obvious when images have to be transmitted or stored. Nevertheless, the above-mentioned methods still have mediocre compression rates, and it is not always possible to achieve any significant reduction in the quantity of data elements needed to represent the image and, at the same time, preserve high quality in this image. These low compression rates lead to problems of memory space in the storage systems or of space requirement in the transmission lines, the passbands of which cannot be extended.